Low dielectric constant materials produced by chemical vapor deposition (CVD) methods are typically used as insulating layers in electronic devices. The electronics industry uses dielectric materials as insulating layers between circuits and components of integrated circuits (IC) and associated electronic devices. Line dimensions are being reduced in order to increase the speed and device density of microelectronic devices (e.g. computer chips). As the line dimensions decrease, the insulating requirements for the interlayer dielectric (ILD) become more rigorous. Shrinking the spacing requires a lower dielectric constant to minimize the RC time constant, where R is the resistance of the conductive line and C is the capacitance of the insulating dielectric interlayer. C is inversely proportional to spacing and proportional to the dielectric constant (k) of the interlayer dielectric (ILD).
Conventional silica (SiO2) CVD dielectric films produced from SiH4 or TEOS (Si(OCH2CH3)4, tetraethylorthosilicate) and O2 have a dielectric constant, k, greater than 4.0. There are several ways in which industry has attempted to produce silica-based chemical vapor deposition (CVD) films with lower dielectric constants, the most successful being the doping of the insulating silicon oxide film with organic groups providing dielectric constants in the range of 2.7-3.5. This organosilicate (OSG) glass is typically deposited as a dense film (density˜1.5 g/cm3) from an silicon-containing precursor, such as an alkylsilane, alkoxysilane, and/or siloxane, in addition to an oxidant, such as O2 or N2O. As increasingly higher device densities and smaller device dimensions require dielectric constant or “k” values to drop below 2.7, the industry has turned to various porous materials for improved insulating properties. The addition of porosity to OSG where the void space has an inherent dielectric constant of 1.0 reduces the overall dielectric constant of the materials. Porous OSG materials are considered to be low k materials because its dielectric constant is less than that of the standard material traditionally used in the industry—undoped silica glass. These materials are typically formed by adding pore-forming species or porogen precursors as reagents during the deposition process and removing the porogen from as-deposited or preliminary materil to provide a porous material. Other materials properties such as mechanical hardness, elastic modulus, residual stress, thermal stability, and adhesion to a variety of substrates depend upon the chemical composition and structure of the porous material or film. Unfortunately, many of these film properties suffer deleterious effects when porosity is added to a film.